Efforts have been made to reduce the cost and size of ink-jet printers and to reduce the cost per printed page. Some of these efforts have focused on developing printers having small, moving print heads that are connected to larger stationary ink reservoirs by flexible ink tubes. This configuration is commonly referred to as “off-axis” printing.
The development of off-axis printing has created the need to precisely control the pressure of the ink at a variety of locations, including the ink reservoir and the print head. Print cartridges may have an internal pressure regulator for regulating the flow of ink from an external source into an ink chamber within the print cartridge. The internal pressure regulator controls the flow of ink into the print cartridge to maintain a relatively constant back pressure at the print head. A relatively constant back pressure may be necessary to prevent the undesired leakage of ink through the print head. This leakage, or drooling, may degrade the quality of printing produced by the printer and may even cause permanent damage to the printer.
Designs utilizing a separate pressure regulator to address these issues may be relatively complicated. In addition, such pressure regulators often have a low tolerance for ingested air, and hence, require special materials to minimize air transmission. In addition, physical contact between the ink and the parts of the regulator sometimes reduce the operating life of the system, due to the corrosive nature of some inks.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.